/**
*      author: Y_Yao
*      created: 2025-01-25 12:50:59
**/

#include<bits/stdc++.h>

#define int LL
using namespace std;
using LL = long long;
const LL LLINF = 1e18;
const int INF = 0x3f3f3f3f;
const int N = 2e5 + 7;
int n,q;
string s;

void solve()
{
    cin >> n >> q;
    cin >> s;
    s = " " + s;
    n = s.size();
    int cnt = 0;
    for(int i = 0;i < (int)s.size() - 2;i++)
    {
        if(s[i] == 'A' && s[i+1] == 'B' && s[i+2] == 'C')
        {
            cnt++;
        }
    }
    while(q--)
    {
        int i;
        char c;
        cin >> i >> c;
        for(int j = max(0ll,i-2);j <= min(n-1,i);j++)
        {
            if(s[j] == 'A' && s[j+1] == 'B' && s[j+2] == 'C')
            {
                cnt--;
            }
        }
        //cout << "cnt :" << cnt;
        s[i] = c;
        for(int j = max(1ll,i-2);j <= min(n-1,i);j++)
        {
            if(s[j] == 'A' && s[j+1] == 'B' && s[j+2] == 'C')
            {
                cnt++;
            }
        }
        cout << cnt << endl;
    }
}

signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);

    int t = 1;
    //cin >> t;
    while(t--)
    {
        solve();
    }
    return 0;
}